Can bus has added another dimension to auto electrics in my experience and it seems like something that you need to deal with regularly in order to retain any learnt expertise. Then there is the equipment required. I was reading something on line about using a OBD breaker box and multimeter to fault check and thought that would be reasonably simple to learn and retain but the cost to me of a box was a bit silly so I wondered how effective that fault finding method would be and if the Mercedes system was the only way to go although it sort of ties you down to that one make. Auto electrics is a pretty complex business now, some seem to have a knack for it, others not so much.